Various researches and studies have been made into the formation of films and fibers from polypeptides, edible saccharides, and living body constituents containing these as main components. Most, however, have ended in industrial failure. The main reason for this is that the starting materials are expensive and the yields of final molded bodies are low, and products having a sufficient mechanical strength are difficult to obtain. As the rare instances of success, in connection with polypeptides, there can be mentioned the utilization of collagen as a casing film for packaging sausage and the formation of dried bean curds from soybeans. A separated soybean protein has been used as a fibrous protein and added to various fish meats and processed meat products. These products, however, have an insufficient mechanical strength, and satisfactory elasticity, strength and elongation characteristics are not manifested.
In connection with edible polysaccharides, various uses of pullulan films have been developed, and as is well known, starch is marketed as a medicine wrapping wafer, oblaat. However, it has been difficult to prepare products having a high mechanical strength from these alone. For example, an oblaat film is heterogeneous and has a poor strength, and even in the presence of a very small amount of moisture, the shape cannot be maintained and the oblaat film cannot properly function as an edible packing material.
To overcome some of these defects, trials have been carried out of adding a cellulose fiber or powder to the above-mentioned polypeptide or edible polysaccharide while the dietary property thereof is noted. For example, Japanese Unexamined Patent Publication No. 51-70873 teaches a process in which a granular cellulose and a protein are mixed by a special method. Furthermore, Japanese Unexamined Patent Publication No. 48-39670 discloses a process in which a chewing gum base is prepared by mixing gluten with granular cellulose. As is well known, a cellulose has an excellent dimensional stability as a regenerated fiber or cellophane, and is used as a starting material for the formation of a product having a satisfactory mechanical strength. But, by adding a fine powder or fine fiber of a cellulose only to the above-mentioned polypeptide or edible polysaccharide, the cellulose component is dispersed as an island component in the polypeptide or edible polysaccharide, and therefore, a prominent improvement of the mechanical strength cannot be expected. When a fine powder or fine fiber of a cellulose is used at too high a content, since the mixture maintains a solid structure inherently possessed by the cellulose, an incompatible taste is given, and in some cases, the cellulose has a bitter taste which remains in the mouth.
As means for improving the mechanical strength of an edible body of the above-mentioned polypeptide or edible polysaccharide by using a cellulose, there may be considered a process in which the cellulose is once dissolved, the desired substance is incorporated in the solution, and the cellulose is regenerated. Although attainment of this object is not intended, Japanese Unexamined Patent Publication No. 51-55355 discloses a process in which in order to obtain a cheap regenerated cellulose film, modified starch is added to a cuprammonium solution or viscose solution of a cellulose. However, incorporation of toxic substances such as by-products derived from a copper ion or carbon disulfide are present in the product described in this publication, and therefore, this process cannot be utilized in the field of food.
We carried out research with a view to overcoming the defects of the above-mentioned polypeptide or edible polysaccharide, that is, (1) brittleness and poor mechanical strength, and (2) a high cost of the starting material, by utilizing a cellulose, and also to overcoming the defects of the cellulose, that is, an incompatible taste remaining in the mouth, by changing the mixed or dispersed state in the polypeptide or edible polysaccharide.